Rotary kiln assemblies



March 12, 1968 F. E. JENSEN 3,

ROTARY KILN ASSEMBLIES Filed Sept. 19, 1966 FIG. 1

j INVENTOR L FLEMMING EDVIN JENSEN 5 W WWIM ATTORNEYS United States Patent Ofilice 3,372,915 Patented Mar. 12, 1968 3,372,915 ROTARY KILN ASSEMBLIES Flemming Edvin Jensen, Copenhagen-Valby, Denmark, assignor to F. L. Smidth & Co., New York, N.Y., a corporation of Delaware Filed Sept. 19, 1966, Ser. No. 580,469 Claims priority, application Great Britain, Sept. 28, 1965, 41,208/65 '7 Claims. (Cl. 263-32) This invention relates to a rotary kiln assembly and more particularly it relates to a rotary kiln assembly having a plurality of cooler tubes mounted in planetary fashion about the kiln at the outlet end thereof, with each tube being connected to the outlet end of the kiln by a communicating chute.

In the operation of a rotary kiln having cooler tubes arranged in planetary fashion thereabout, hot material falls or slides through the outlet openings in the kiln into the communicating chutes and into the cooler tubes which are lowermost at that time. Air is drawn or blown through the cooler tubes in countercurrent to the hot material so as to cool the material; this air becomes heated and subsequently enters the kiln through the communicating chutes as preheated air to support combustion in the kiln.

These cooler tubes are arranged to extend from their inlets in a direction toward either the inlet or the outlet end of the kiln, and they are arranged parallel to or inclined at an angle to the axis of the kiln. It is also common to include scoops, chains or other devices in the cooler .tubes for urging the material toward their outlet ends. With cooler tubes of this kind, there is often a tendency for some of the hot material that has entered a tube when it was below the axis of the kiln to return to the kiln again when the tube reaches a position above the axis, because in this position the outlets of the communicating chutes are above their inlets. This return of material is very undesirable, not only because it reduces the output but because it also hinders the free passage of the preheated air into the kiln.

Several constructions have been proposed for avoiding this return of material to the kiln. In one construction the chutes are curved and formed as a part of a spiral. In another, the inlet ends of the cooler tubes are made conical or otherwise so formed as to offer an inclined surface over which the hot material may fall by gravity at all positions of the tube during the rotation of the kiln. Both constructions help to prevent the material which has entered the cooler tubes from returning to the kiln through the chutes, but there is heavy wear on the curved chutes or on the conical end sections of the cooler tubes, caused by the direct impact of the hot material. This wear necessitates repair work that repeatedly interrupts the treament of material in the kiln.

It is a purpose of the invention to prevent the return of material to the kiln without exposing the end sections of the cooler tubes to undue wear. According to the invention, the inlet end of each tube has a first portion opposite the outlet end of the respective connected chute which is an extension of the cylindrical Wall of the tube and a second portion that is nearer the kiln which is formed as a section of a cylinder, the axis of which is so inclined to that of the tube as to provide a surface down which material in the tube can slide away from the outlet of the chute when the tube is above the kiln axis. The chute enters this latter part at a point offset in the direction of rotation of the kiln from the plane of symmetry of the second portion.

Because of the rotation of the kiln, the material in the kiln mostly or wholly lies on one side of the central diametrical plane, so for the most part the material will start to flow into the cooler tube immediately after the outlet opening from the kiln to the communicating chute has passed the lowermost point in its circular path. As the tube moves upward, the material slides down the sloping end surface away from the inlet opening. Although there is a general movement of the material along the tube away from the outlet of the chute, some of the material in the tube slides back again for a limited time as the tube moves downward again below the kiln axis so as to form a cushion onto which the next charge of material for the tube falls. This cushion of accumulated material protects the tube below the inlet opening against the impact of the charge of hot material. When the tube moves upward again, the cushion, together with the layer of fresh material now covering it, moves away from the inlet. The cushion thus continuously moves forward and backward in timed relation with the position of the cooler tube.

The diameter of the section of the cylinder which forms the sloping end surface is preferably the same as that of the cooler tube. Not only does this simplify construction which then only entails cutting and welding, but it also enhances even transfer of material from the sloping end surface of the cooler tube.

Advantageously, the angle formed between the axes of the cooler tube and of the cylindrical section that forms the sloping end surface is from 40 to 50 degrees, as this is found to ensure the most effective transport of the material away from the inlet opening of the tube.

Under extremely high loading of the cooler, the risk of return of material to the kiln is further reduced if each communicating chute is a straight pipe projecting into the interior of the tube. However, as mentioned above, the material starts falling into the chute when the chute inlet has passed its lowermost point, so the material will thus, if allowed, fall freely into the cooler tube along a curved path. In order to ensure that straight chutes are exposed to the lowest possible wear, each chute should also be rearwardly inclined in the direction of rotation from its inlet to its outlet, and in fact the angle between its axis and the plane that contains the axes of the kiln and the tube is preferably from 15 to 25 degrees.

A preferred embodiment of the invention is described hereinbelow with reference to the drawings wherein:

FIGURE 1 is a side elevation of part of the kiln and part of a cooler tube with a communicating chute below the kiln;

FIGURE 2 is a section on the line 22 in FIGURE 1;

FIGURE 3 is a section to a larger scale on the line 33 in FIGURE 1; and

FIGURE 4 is an elevation similar to FIGURE 1, but with the cooler tube above the kiln.

Part of a rotary kiln 10 is shown in the drawings for burning a charge 11 of, for instance, cement raw material to clinker. The kiln 10 has outlet openings 12 for the discharge of the hot material, and these are connected by communicating chutes 13 to cooler tubes 14 which are mounted around the kiln shell in planetary fashion.

Each cooler tube 14 is cylindrical throughout the greater part of its length, only its inlet end being shown in FIGURE 1. At the inlet end shown, a. first portion 15 of the tube remote from the kiln is part of the cylindrical wall of the tube, but a second portion 16 nearer the kiln is a section of an inclined cylinder. The diameter of the cylinder of which the second portion 16 is a section is the same as that of the tube 14. The axis of this part is shown at X, and it makes an angle A with the axis Y of the tube, this angle in the example shown being about 45 degrees. As shown in FIGURE 3, the second portion 16 is not symmetrical about the plane Z which contains the axis U of the kiln and the axis Y of the cooler tube, but rather leads the plane of symmetry of the second portion 16 3 shown by a line W, in the direction of rotation of the kiln by an angle B of from 5 to degrees.

Each chute 13 is a straight tube which communicates with an opening 17 in the second portion 16 of the corresponding tube 14. The opening 17 is offset in the direction of rotation from the plane W, and the chute 13 is inclined rearwardly in the direction of rotation of the kiln from its inlet to its outlet as shown, the angle C its axis makes with the plane Z being from to degrees. Thus, the angle D, which is equal to the angle C minus the angle W, is from 10 to 20 degrees. The chutes 13 can as shown at 18 in FIGURE 4 project into the cooler tubes so that under extremely high rates of fiow through the coolers an additional safeguard is provided against the return of flow of material to the kiln.

The hot clinker or other material in the kiln is carried round by the kiln so that it does not lie on the bottom of the kiln on each side of the plane Z but rather takes up the position shown at 11 in FIGURE 2. In consequence it is not until each opening 12 in the kiln has passed through the plane Z that material starts to fall through the chute 13 into the tube 14. Because the chute 13 is inclined to the plane Z, the material hardly touches the walls of the chute but instead falls directly into the tube 14. As the kiln continues to rotate, material will continue to slide into the tube 14, often throughout an angular movement of the kiln of from to 40 degrees.

As the kiln rotates, material 19 in the cooler tube will of course move round the inner surface of the tube. Having initially fallen onto the straight first portion 15 of the inlet end of the tube, it will slide onto the inner surface of the second portion 16 when the tube passes above the axis of the kiln, as shown in FIGURE 4. At this stage it will further slide down the inner surface of the part 16 away from the inlet opening 17 and towards the outlet of the cooler tube.

When the cooler tube in the course of the further rotation of the kiln again passes below the axis of the kiln on the opposite side of the kiln part of the charge 19 in it will start to slide backward, toward the inlet end and form a. cushion. By the time the tube reaches its lowermost position, this cushion of material will cover first portion 15 of the tube below the opening 17 and protect the tube against the impact of the hot material which now begins to enter the tube.

The chute 13 may be a steel tube with a ceramic or other heat-insulating lining.

An internal dam ring may be built into the kiln to stop the forward movement of the material through the kiln just beyond the inlets to the chute 13 so that the material builds up a little in the kiln and falls through the chutes 13 in a direction substantially at right angles to the kiln axis and with no remaining forward component of movement.

I claim:

1. In a rotary kiln assembly having an outlet end from which the material is discharged, the improvement in combination therewith comprising a plurality of generally cylindrical cooler tubes mounted about the kiln :at the inlet end thereof, a communicating chute interconnecting the kiln with each tube for transfer of material from the kiln to the tubes with the outlet end of the chute opening into the inlet end of the tube, the inlet end of each tube having a first portion opposite the outlet end of the respective connected chute which is an extension of the cylindrical wall of the tube and a second portion nearer the kiln than the first portion which is a section of a cylinder, the axis of which is inclined with respect to the axis of the tube to form an inclined surface down which material in the cooler tube can slide away from the outlet of the chute when the cooler tube is above the kiln axis, and the outlet of the chute is received in the second inclined cylindrical portion at a point offset in the direction of rotation of the kiln from the plane of symmetry of the second portion.

2. The assembly according to claim 1 in which the section of the cylinder is of the same diameter as the cooler tube.

3. The assembly according to claim 1 in which the angle between the axis of the cooler tube and the axis of the section of the cylinder is from 40 to degrees.

4. The assembly according to claim 1 in which each communicating chute is a straight pipe communicating with the interior of the cooler tube.

5. The assembly according to claim 4 in which the axes of the chutes lie in a plane which is perpendicular to the axis of the kiln and each chute axis is rearwardly inclined in the direction of rotation from its inlet end to its outlet end.

6. The assembly according to claim 5 in which the angle between the axis of the chute and the plane containing the axes of the kiln and the cooler is from 15 to 25 degrees.

7. The assembly according to claim 1 in which the plan of symmetry of the section of the cylinder makes an angle of from 5 to 10 degrees with the plane containing the axes of the kiln and the tube.

References Cited UNITED STATES PATENTS 828,555 8/1906 Krottnaurer 263-32 2,136,174 11/ 1938 Vogel-Jorgensen 26332 3,279,775 10/1966 Roubal 263--32 CHARLES I. MYHRE, Primary Examiner.

A. D. HERRMANN, Assistant Examiner. 

1. IN A ROTARY KILN ASSEMBLY HAVING AN OUTLET END FROM WHICH THE MATERIAL IS DISCHARGED, THE IMPROVEMENT IN COMBINATION THEREWITH COMPRISING A PLURALITY OF GENERALLY CYLINDRICAL COOLER TUBES MOUNTED ABOUT THE KILN AT THE INLET END THEREOF, A COMMUNICATING CHUTE INTERCONNECTING THE KILN WITH EACH TUBE FOR TRANSFER OF MATERIAL FROM THE KILN TO THE TUBES WITH THE OUTLET END OF THE CHUTE OPENING INTO THE INLET END OF THE TUBE, THE INLET END OF EACH TUBE HAVING A FIRST PORTION OPPOSITE THE OUTLET END OF THE RESPECTIVE CONNECTED CHUTE WHICH IS AN EXTENSION OF THE CYLINDRICAL WALL OF THE TUBE AND A SECOND PORTION NEARER THE KILN THAN THE FIRST PORTION WHICH IS A SECTION OF A CYLINDER, THE AXIS OF WHICH IS INCLINED WITH RESPECT TO THE AXIS OF THE TUBE TO FORM AN INCLINED SURFACE DOWN WHICH MATERIAL IN THE COOLER TUBE CAN SLIDE AWAY FROM THE OUTLET OF THE CHUTE WHEN THE COOLER TUBE IS ABOVE THE KILN AXIS, AND THE OUTLET OF THE CHUTE IS RECEIVED IN THE SECOND INCLINED CYLINDRICAL PORTION AT A POINT OFFSET IN THE DIRECTION OF ROTATION OF THE KILN FROM THE PLANE OF SYMMETRY OF THE SECOND PORTION. 